JP7301692B2 - Power supply and image forming apparatus - Google Patents

Description

The present invention relates to a power supply and an image forming apparatus, and more particularly to an image forming apparatus using a transformer type high voltage power supply.

With respect to high-voltage power supplies, conventionally, there has been proposed a method of controlling a transformer using a table that associates the output voltage of the transformer with the frequency of the drive pulse signal (see, for example, Patent Document 1). On the other hand, another conventional example proposes a method of controlling a transformer using a memory that stores information about the duty of a drive pulse signal corresponding to the output voltage of the transformer (see, for example, Patent Document 2).

JP-A-2008-224778 JP 2004-040911 A

Normally, when the transformer is controlled by the frequency of the drive pulse signal, the output voltage becomes a peak value at a predetermined frequency, and a higher voltage cannot be output. Further, when the transformer is controlled by the duty of the drive pulse signal, the transformer may saturate when the ON width increases to a predetermined width, or the power of the field effect transistor (FET) that is turned on/off by the drive pulse signal may increase. do. Therefore, it is necessary to set the ON width to a predetermined value or less. In this way, when the transformer is controlled by the frequency or duty of the drive pulse signal, there are restrictions on the variable width of the output voltage. Therefore, in order to further widen the range of the output voltage, a higher output transformer and a higher power FET are required, which raises the problem of increasing the cost and size of the device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-cost structure that suppresses the influence of variations in the inductance of a transformer and enables output in a wide voltage range. do.

In order to solve the above problems, the present invention has the following configurations.

(1) a transformer having a primary winding and a secondary winding; and a voltage applied to the primary winding of the transformer, which is connected to the primary winding and turned on or turned on according to an input pulse signal. and a control means for outputting the pulse signal to the switching element to control driving of the transformer, wherein an output voltage corresponding to the voltage induced in the secondary winding of the transformer is provided. A power supply device for outputting, comprising storage means for storing information associating the output voltage with the duty and frequency of the pulse signal, wherein the control means controls the output voltage and the information stored in the storage means. A power supply device characterized by switching the frequency and/or the duty based on.

(2) an image carrier; charging means for charging the image carrier; exposure means for forming an electrostatic latent image on the image carrier charged by the charging means; A power supply device comprising: developing means for developing an electrostatic latent image to form a toner image; transfer means for transferring the toner image on the image carrier onto a recording material; and the power supply device according to (1). (2) an image forming apparatus, wherein the output voltage is supplied to at least one of the charging means, the developing means and the transfer means;

According to the present invention, it is possible to suppress the influence of variation in the inductance value of the transformer and to output in a wide voltage range with an inexpensive configuration.

Block diagram of power supply unit of embodiment 1 FIG. 4 shows output characteristics of transformers of Examples 1 to 4; A block diagram of a power supply unit of Embodiment 2, and a diagram showing output characteristics of a transformer. FIG. 10 is a diagram showing output waveforms of the power supply unit according to the second embodiment; Block diagram of power supply unit of embodiment 3 Schematic cross-sectional view of an image forming apparatus of Example 4

Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, the components described in this embodiment are merely examples, and the scope of the present invention is not intended to be limited to them.

[Power supply]
FIG. 1 shows a block diagram and a circuit diagram of a high-voltage power supply device according to a first embodiment. The high-voltage power supply device includes a power supply unit 100 that generates high voltage and a CPU 3 that controls the power supply unit 100 . The power supply unit 100 includes a resistor 110, a smoothing capacitor 101, a field effect transistor (hereinafter referred to as FET) 102 which is a switching element, a transformer 103 having a primary winding and a secondary winding, a high voltage diode 105, and a high voltage capacitor 106. have.

CPU 3 outputs drive signal S 201 to power supply unit 100 via resistor 110 . The power supply unit 100 switches the voltage applied to the primary winding of the transformer 103 (the voltage Vc (the voltage of the smoothing capacitor 101)) by intermittently switching the FET 102 according to the drive signal S201. That is, the FET 102 is connected to the primary winding and turns on or off the voltage applied to the primary winding of the transformer 103 according to the input drive signal S201, which is a pulse signal. The CPU 3 outputs a drive signal S201 to the FET 102 to control driving of the transformer 103 . As a result, the power supply unit 100 increases the switched voltage and outputs it to the secondary winding of the transformer 103 . The increased voltage is rectified and smoothed by a high voltage diode 105 and a high voltage capacitor 106 to generate a high DC voltage. Thus, the power supply unit 100 outputs an output voltage corresponding to the voltage induced in the secondary winding of the transformer 103. FIG.

The high DC voltage can be adjusted by changing the frequency and duty of the drive signal S201. The power supply unit 100 also includes a non-volatile memory 150 as storage means, and the CPU 3 controls the non-volatile memory 150 using a communication method such as the I2C method.

The power supply unit 100 of Example 1 does not have means for feeding back the generated high voltage DC voltage. In a circuit configuration in which a high DC voltage is not fed back, the output characteristics differ depending on the inductance value of the transformer 103 . The inductance value of the transformer 103 naturally occurs due to manufacturing variations.

[Power supply unit output characteristics]
FIG. 2(a) shows high voltage output characteristics with respect to on-duty (hereinafter simply referred to as duty) of the drive signal S201 in the power supply unit 100 of FIG. Note that the duty of the drive signal S201 may be controlled by off-duty. In FIG. 2(a), the horizontal axis indicates duty, and the vertical axis indicates high DC voltage (hereinafter also referred to as output voltage).

The transformer 103 uses three transformers with different inductance values caused by manufacturing variations, and the respective inductance values (hereinafter referred to as L values) are Lmin, Ltyp, and Lmax (Lmin<Ltyp<Lmax). Assume that the frequency f of the drive signal S201 is f1 and the load impedance is R. The output voltage when the duty is D has different values depending on the transformer 103, as shown in FIG. 2(a). Specifically, when the duty of the drive signal S201 is D, the output voltage of the transformer 103 with an L value of Lmin is VLmin. When the duty of the drive signal S201 is D, the output voltage of the transformer 103 whose L value is Ltyp is VLtyp. When the duty of the drive signal S201 is D, the output voltage of the transformer 103 with an L value of Lmax becomes VLmax. Note that the relationship VLmin<VLtyp<VLmax holds.

Thus, when controlling the output voltage to a constant value in a circuit configuration that does not perform feedback control, the frequency f and the duty D of the drive signal S201 are adjusted for each device in consideration of variations in the L value of the transformer 103. There is a need to. As a method therefor, a method of measuring the output characteristics of the power supply unit 100 in advance and storing them in the nonvolatile memory 150 or the like is known. Output characteristics are measured, for example, in the production line of the power supply unit 100 . By measuring the output characteristics of the power supply unit 100 in advance in this way, it is possible to control the output voltage to an arbitrary value regardless of variations in the L value of the transformer 103 .

[Relationship between drive signal and output characteristics]
The high-voltage output characteristic shown in FIG. 2(b) indicates the output voltage when the frequency f and the duty D of the drive signal S201 are changed in the power supply unit 100 of FIG. The horizontal axis represents the duty D of the drive signal S201, and the vertical axis represents the output voltage, respectively, showing the output characteristics when the frequencies of the drive signal S201 are set to f1 and f2 (>f1). Note that the load impedance is a constant value R. In general, in a high-voltage inverter transformer, if the duty of the drive signal is made too large, the transformer will saturate or the power consumption of the FET will increase. Therefore, it is necessary to set the duty value of the drive signal to a duty value that ensures safety. Also, if the duty of the drive signal is made too small, the output characteristics may become unstable, so it is necessary to set the duty to a value that allows stable control.

From these points of view, allowable minimum and maximum duties D are defined as Dmin and Dmax, respectively. In this case, as shown in FIG. 2B, when the frequency f of the driving signal S201 is f1, the output voltage at the minimum duty Dmin is V1min, and the output voltage at the maximum on-duty Dmax is V1max. . When the frequency f of the driving signal S201 is f2, the output voltage at the minimum duty Dmin is V2min, and the output voltage at the maximum duty Dmax is V2max. Then, when the frequency f of the drive signal S201 is f1, the voltage range that can be output is V1min to V1max. On the other hand, when the frequency f of the drive signal S201 is f2, the voltage range that can be output is V2min to V2max.

Here, at load impedance R, the range of output voltage values guaranteed as the output capability of power supply unit 100 (hereinafter referred to as guaranteed output range) is Vx to Vy. For example, the minimum value Vx of the guaranteed output range is between V1min and V2min (V1min≦Vx≦V2min), and the maximum value Vy of the guaranteed output range is between V1max and V2max (V1max≦Vy≦V2max). When the frequency f of the driving signal S201 is f1, Vy>V1max, so that the high voltage side cannot be output. Conversely, when the frequency f of the driving signal S201 is f2, it becomes impossible to output the low voltage side because Vx<V2min.

Therefore, the frequency f of the driving signal S201 is set to f1 when outputting an output voltage of V2min or less, and the frequency f of the driving signal S201 is set to f2 when outputting a voltage of V1max or more. This makes it possible to satisfy the required output range. The range of V2min or more and V1max or less may be selected arbitrarily because the frequency f of the driving signal S201 can be output at either frequency f1 or f2.

As described above, by variably controlling both the frequency f and the duty D of the drive signal S201, it is possible to widen the output range of the high voltage and to meet a wide range of required specifications. As another means for widening the output range, there are methods such as using a high-output transformer and using an input voltage adjustment circuit. It can be said that it is a means that can be realized with a simple configuration.

[Method for selecting drive signal frequency and duty]
Next, a method of selecting the frequency f and the duty D of the drive signal S201 using the information (table) stored in the nonvolatile memory 150, which is the feature of the first embodiment, will be described. The nonvolatile memory 150 stores in advance a table that is information representing the characteristics of the output voltage of the power supply unit 100 .

表１は、不揮発性メモリ１５０に記憶されているテーブルの一例を示している。テーブルは、出力電圧と、その出力電圧を出力するための駆動信号Ｓ２０１のデューティ（Ｄｕｔｙ）及び周波数ｆとの対応関係が定義されている。例えば、出力電圧Ｖｍｉｎに関連付けて、駆動信号Ｓ２０１のデューティＤｍｉｎ、周波数ｆ１が関連付けられている。電源ユニット１００の出力電圧は、駆動信号Ｓ２０１のデューティＤが大きいほど高くなり、駆動信号Ｓ２０１の周波数ｆが高いほど高くなる。

Table 1 shows an example of a table stored in the nonvolatile memory 150. The table defines the correspondence relationship between the output voltage and the duty and frequency f of the drive signal S201 for outputting the output voltage. For example, the output voltage Vmin is associated with the duty Dmin of the drive signal S201 and the frequency f1. The output voltage of the power supply unit 100 increases as the duty D of the drive signal S201 increases, and increases as the frequency f of the drive signal S201 increases.

The contents of the table will be specifically described below in correspondence with the output characteristics of FIG. 2(b). The range of the output voltage is V1min to V2max, the frequency f corresponding to the minimum value V1min of the output voltage is f1, and the duty D is Dmin. In a region where the output voltage is low, the frequency f of the driving signal S201 is fixed at f1, and the duty D is set to D1, V1, V2 (>V1), . D2 (>D1) . . .

When the output voltage reaches V2min, the frequency f of the driving signal S201 is switched to f2, and the duty D is reset to Dmin. In the region where the output voltage is V2min or more, the frequency f of the drive signal S201 is fixed at f2, and the duty D changes to D1, D2, . The frequency f corresponding to the maximum value V2max of the output voltage is f2, and the duty D is Dmax.

The CPU 3 communicates with the non-volatile memory 150 and refers to the table of Table 1 stored in the non-volatile memory 150 . The CPU 3 selects the frequency f and the duty D of the drive signal S201 from the table according to the output voltage supplied by the power supply unit 100 to the load of the image forming apparatus. Then, the CPU 3 controls the driving signal S201 with the selected frequency f and duty D to generate an arbitrary output voltage.

In Table 1, switching of the frequency f of the drive signal S201 is performed at the timing when the output voltage reaches V2min. As described above, in the region where the output voltage is between V2min and V1max, the frequency f of the driving signal S201 may be either f1 or f2. Therefore, the frequency f of the drive signal S201 may be switched from f1 to f2 when the output voltage is V1max (the duty D is Dmax). In this case, the duty of the drive signal S201 is reset to a duty (>Dmin) corresponding to the output voltage V1max at the frequency f2.

Thus, the following information is set in the table of Table 1 of the first embodiment. That is, a first frequency f1 corresponding to the first voltage range V1min to V2min and a second voltage range continuous to the first voltage range V2min to V2max corresponding to the first frequency f1. A second frequency f2 higher than the frequency is set. When changing the output voltage within the first voltage range, the CPU 3 changes the duty D of the driving signal S201 while selecting f1 as the frequency f of the driving signal S201. Further, when changing the output voltage within the second voltage range, the CPU 3 changes the duty D of the drive signal S201 with f2 selected as the frequency f of the drive signal S201.

As described above, according to the first embodiment, it is possible to provide a power supply device that has a low cost structure, is not affected by variations in the inductance value of the transformer, and is compatible with a wide range of output voltages. In the table described in the first embodiment, the frequency f of the drive signal S201 has two levels of f1 and f2, but may have three levels or more. Furthermore, although the frequency f is switched and the table corresponding to the output voltage and the duty D in each region has been described, the relationship between the frequency f and the duty D may be reversed. That is, the duty D may be switched in a plurality of regions, and a table may be provided in which the output voltage and the frequency f are associated with each region.

That is, the table of Table 1 may include the following information. A first duty corresponding to the first voltage range and a second duty greater than the first duty corresponding to a second voltage range continuous with the first voltage range may be set. . When changing the output voltage within the first voltage range, the CPU 3 changes the frequency f of the driving signal S201 while selecting the first duty as the duty D of the driving signal S201. Further, when changing the output voltage within the second voltage range, the CPU 3 changes the frequency f of the drive signal S201 while selecting the second duty as the duty D of the drive signal S201. For these modified examples, an appropriate table configuration should be selected according to the characteristics of the transformer and the circuit configuration. Thus, the nonvolatile memory 150 stores information that associates the output voltage of the power supply unit 200 with the duty and frequency of the drive signal S201. The CPU 3 switches the frequency or duty of the drive signal S201 based on the output voltage and a table that is information stored in the nonvolatile memory 150 .

As described above, according to the first embodiment, it is possible to suppress the influence of variation in the inductance value of the transformer and to enable output in a wide voltage range with an inexpensive configuration.

[Power supply]
FIG. 3(a) shows a block diagram and a circuit diagram of the power supply unit 200 of the second embodiment. The power supply unit 200 shown in FIG. 3A has the advantage that the number of parts is small and the feedback control can be performed with an inexpensive configuration. On the other hand, the power supply unit 200 has a problem that ripples in the output voltage are likely to occur. In a second embodiment, a method of suppressing ripples in the output voltage using a table stored in the nonvolatile memory 150 will be described.

[Feedback control]
First, regarding the circuit operation, the drive control of the transformer 103 is the same as that of the first embodiment, so the description is omitted, and the feedback control will be described. A feedback section 210 as feedback means has a comparator 108 , resistors 107 , 109 and 111 and a capacitor 112 . In the feedback unit 210, the PWM signal S202 from the CPU 3 is smoothed by the resistor 111 and the capacitor 112, becomes a DC voltage corresponding to the duty of the PWM signal S202, and is input to the + input terminal (non-inverting input terminal) of the comparator 108. . The duty of the PWM signal S202 becomes the target value of the output voltage of the power supply unit 200, and the duty of the PWM signal S202 and the output voltage have a proportional relationship. That is, the longer the duty of the PWM signal S202, the higher the output voltage.

A negative input terminal (inverted input terminal) of the comparator 108 is supplied with a feedback voltage obtained by stepping down the output voltage by the resistor 107 and dividing it by the reference voltage Vr, the resistors 107 and 109 . When the output voltage increases and the feedback voltage input to the -input terminal of the comparator 108 exceeds the target voltage input to the +input terminal, the output of the comparator 108 becomes low level and the gate voltage of the FET 102 becomes 0V. . This state is referred to as "a state in which the drive signal S201 is thinned out". When the driving signal S201 is thinned out, the driving of the transformer 103 is stopped and the output voltage is lowered. Thus, the feedback section 210 stops the driving of the transformer 103 by the FET 102 regardless of the drive signal S201 when the feedback voltage is higher than the target value. Afterwards, when the feedback voltage drops below the target voltage, FET 102 resumes oscillation and the output voltage increases again. By repeating such operations, the output voltage is maintained.

Since the power supply unit 200 of the second embodiment operates in this manner, ripples are likely to occur in the output voltage. Furthermore, the output voltage ripple has a correlation with the target output voltage (hereinafter referred to as target output voltage). 3B and 4 show the output characteristics and output waveform of the power supply unit 200, respectively. In FIG. 3B, the horizontal axis indicates the duty of the drive signal S201, and the vertical axis indicates the output voltage of the power supply unit 200. FIG. 4A shows waveforms when the output voltage is V(a), and FIG. 4B shows waveforms when the output voltage is V(b) (<V(a)). Specifically, in FIGS. 4A and 4B, (i) shows the waveform of the driving signal S201, and (ii) shows the output voltage of the power supply unit 200. FIG. Note that (ii) indicates the target output voltage (output target value) with a dashed line.

From FIG. 3B, when the frequency f of the drive signal S201 is f1 and the duty is D, the maximum output voltage of the power supply unit 200 is VLmax. Here, in FIG. 3B, the transformer 103 with a load impedance of R and an L value of Lmax is used. When the target output voltage is V(a) close to the maximum output voltage VLmax, as shown by the waveform of FIG. 4A, the output voltage ripple is small because the drive signal S201 is thinned out less. On the other hand, when the target output voltage is V(b), which is lower than V(a), as shown in the waveform of FIG. ripple becomes large.

That is, in order to suppress ripples in the output voltage, the frequency f and duty D of the drive signal S201 should be adjusted to reduce the difference between the output voltage of the power supply unit 200 and the target output voltage. Ideally, the output voltage should be equal to the target output voltage, and driving should be performed in a state in which the drive signal S201 is not thinned out at all. However, it is conceivable that the output characteristics of the power supply unit 200 change due to the influence of variations in the load of the components of the image forming apparatus, load fluctuations due to environmental temperature and humidity, and the like. Considering the possibility that the output capacity of the power supply unit 200 may be insufficient due to this influence, it is preferable to set the driving condition to give the output capacity slightly higher than the target output voltage.

Next, a method of applying the output characteristic table of the present invention to the power supply unit 200 of the second embodiment will be described. As described in the first embodiment, the output characteristics of the power supply unit 200 also vary due to variations in the inductance value of the transformer 103 . If there are variations in the output characteristics shown in FIG. 2A, it is necessary to set the values of the frequency f and the duty D of the drive signal S201 so that the target output voltage can be output even at Lmin. However, when a component whose inductance value is Lmax is driven with the same set value, the difference between the output voltage and the target output voltage becomes large, and the ripple of the output voltage also becomes large.

Therefore, by storing the output characteristic table of the power supply unit 200 in advance in the nonvolatile memory 150, it is possible to select an appropriate frequency f and duty D according to the variation of the inductance value. can be suppressed. Since the contents of the table and the control method are the same as those of the first embodiment, the description thereof is omitted.

As described above, according to the second embodiment, it is possible to provide a high-voltage power supply device that suppresses ripples in the output voltage while maintaining a low-cost circuit configuration that keeps the output voltage constant by thinning out the drive signals. becomes. As described above, according to the second embodiment, it is possible to suppress the influence of variation in the inductance value of the transformer and to output in a wide voltage range with an inexpensive configuration.

In Embodiments 1 and 2, the method of selecting an appropriate drive condition by storing the output characteristic tables of the power supply units 100 and 200 in advance in the nonvolatile memory 150 has been described. These are based on the premise that the load on the image forming apparatus can also be predicted in advance. For example, loads such as paper and a photosensitive drum are determined for charging processing, and paper and transfer rollers are determined for transfer processing. Therefore, the load on the image forming apparatus can be predicted to some extent. However, as described above, the resistance value of the load changes depending on the variation in the parts, the environmental temperature/humidity, the moisture absorption state of the paper, etc. Therefore, it is necessary to consider the variation in the resistance value of the load in the design. Therefore, in a third embodiment, a method of monitoring the resistance of the load using a load current detection circuit and setting appropriate driving conditions will be described.

[Power supply]
FIG. 5 shows a block diagram and a circuit diagram of a power supply unit 300 according to the third embodiment. Since the drive control of the transformer 103 is the same as that of the first embodiment, the description is omitted, and the load current detection circuit 350, which is the detection means for detecting the current flowing through the load, will be described. The load current detection circuit 350 has resistors 113 , 114 , 116 and 117 and an operational amplifier 115 .

A current flowing through the secondary side of the transformer 103 is supplied from the power supply unit 300 to the load of the image forming apparatus, and returns from the GND of the operational amplifier 115 to the transformer 103 through the resistors 113 and 114 . Therefore, if the voltage difference across resistor 114 is known, the load current can be calculated. The voltage of the + input terminal of the operational amplifier 115 is known because it is determined by dividing the voltage Vr by the resistors 116 and 117 . Also, since the voltage between the resistors 113 and 114 is connected to the AD port of the CPU 3, the CPU 3 can calculate the load current value from the AD value input to the AD port.

[Output characteristic table]
Table 2 shows the contents of the output characteristic table of the third embodiment. A plurality of tables corresponding to load current values are stored in advance in the nonvolatile memory 150 . These tables offset changes in output characteristics caused by load fluctuations by changing the frequency f of the drive signal S201.

表２のテーブル１、テーブル２、テーブル３は、それぞれ実施例１の表１で説明したテーブルと同様の情報を有している。不揮発性メモリ１５０は、負荷に流れる電流に応じたテーブル１～３を複数記憶している。なお、テーブル１では周波数ｆをｆ１１とｆ１２（＞ｆ１１）で切り替える。テーブル２では周波数ｆをｆ２１とｆ２２（＞ｆ２１）で切り替える。テーブル３では周波数ｆをｆ３１とｆ３２（＞ｆ３１）で切り替える。

Table 1, Table 2, and Table 3 of Table 2 each have the same information as the table described in Table 1 of the first embodiment. The nonvolatile memory 150 stores a plurality of tables 1 to 3 corresponding to the current flowing through the load. In Table 1, the frequency f is switched between f11 and f12 (>f11). In Table 2, the frequency f is switched between f21 and f22 (>f21). In Table 3, the frequency f is switched between f31 and f32 (>f31).

The CPU 3 selects Table 1 if the result of load current detection by the load current detection circuit 350 is less than I1 (load current<I1). CPU 3 selects table 2 if the result of load current detection by load current detection circuit 350 is greater than or equal to I1 and less than I2 (I1≦load current<I2). The CPU 3 selects Table 3 if the result of load current detection by the load current detection circuit 350 is equal to or greater than I2 (I2≦load current). In this manner, the CPU 3 selects one table from among the plurality of tables 1 to 3 stored in the nonvolatile memory 150 according to the current detected by the load current detection circuit 350, and determines the duty D and frequency of the drive signal S201. Set f. Based on the selected table, the CPU 3 controls the drive signal S201 under the conditions (output voltage and frequency for duty) set in the table.

In addition, although the table in which the frequency f is changed with respect to the difference in the load current is used in the third embodiment, the present invention is not limited to this. It is also possible to change the duty D of the drive signal S201 to cope with this, or to change both the frequency f and the duty D to create a plurality of tables. Also, in Table 2, three tables are selected according to the load current value, but the number of tables is arbitrary. The contents and number of these tables may be appropriately selected for each apparatus according to the load characteristics of the power supply unit 300, the variation in the load resistance of the image forming apparatus, the required high voltage output accuracy, and the like.

In addition, in the third embodiment, a method of actually monitoring the load current by the load current detection circuit 350 has been described. is also possible. In this case, the non-volatile memory 150, which is storage means, stores a plurality of tables corresponding to temperature and/or humidity. The CPU 3 may select an appropriate table from a plurality of tables stored in advance in the non-volatile memory 150 according to the environmental temperature and humidity based on the detection result of the sensor. That is, the CPU 3 selects one table from among a plurality of tables stored in the nonvolatile memory 150 according to temperature and/or humidity, and sets the duty D and frequency f of the drive signal S201. As described above, according to the third embodiment, there is provided a high-voltage power supply capable of stably controlling the output voltage with a low-cost configuration even when the output characteristics of the high-voltage power supply change due to the influence of load variations. be able to. The load current detection circuit (monitor) and sensor described in the third embodiment can also be applied to the circuit for thinning out the driving signal S201 described in the second embodiment, and any combination thereof is possible.

As described above, according to the third embodiment, it is possible to suppress the influence of variation in the inductance value of the transformer and to enable output in a wide voltage range with an inexpensive configuration.

The power supply units 100, 200, and 300 of Examples 1 to 3 can be applied, for example, as a high-voltage power supply device used in an electrophotographic image forming apparatus such as a laser printer. The high voltage power supply supplies a high voltage to a load that requires a high voltage in the image forming means of the image forming apparatus. For example, it includes a charging section that charges the image carrier, a developing section that develops a latent image formed on the image carrier, and a transfer section that transfers a toner image formed on the image carrier to a recording material. The image forming apparatus will be described below.

[Explanation of laser beam printer]
FIG. 6 shows a schematic configuration of a laser beam printer as an example of an image forming apparatus. A laser beam printer 1000 (hereinafter referred to as printer 1000 ) includes a photosensitive drum 1010 , a charging section 1020 and a developing section 1030 . A photosensitive drum 1010 is an image carrier on which an electrostatic latent image is formed. A charging unit 1020 that is a charging unit uniformly charges the photosensitive drum 1010 . An exposure device 1025, which is exposure means, forms an electrostatic latent image on the photosensitive drum 1010 according to input image data. A developing unit 1030, which is a developing means, forms a toner image by developing the electrostatic latent image formed on the photosensitive drum 1010 with toner. A toner image formed on the photosensitive drum 1010 (on the image bearing member) is transferred onto a sheet P as a recording material supplied from a cassette 1040 by a transfer unit 1050 as transfer means. The unfixed toner image transferred to the sheet P is fixed by a fixing device 1060 serving as fixing means, and is discharged onto a tray 1070 . The photosensitive drum 1010, charging section 1020, developing section 1030, and transfer section 1050 constitute an image forming section.

The printer 1000 also includes a power supply device 1080 , and supplies power from the power supply device 1080 to a driving unit such as a motor and the control unit 5000 . The power supply device 1080 has the power supply unit 100, the power supply unit 200, or the power supply unit 300 of the first to third embodiments. The power supply unit 100 , the power supply unit 200 or the power supply unit 300 supplies a high voltage as an output voltage to at least one of the charging section 1020 , the developing section 1030 and the transfer section 1050 . The control unit 5000 has a CPU3. The table of Table 1 or Table 2 of the frequency f and the duty D of the drive signal S201 corresponding to the output voltage of the transformer 103 is stored in the nonvolatile memory 150 of the power supply unit 100, power supply unit 200, or power supply unit 300. The CPU 3 controls the transformer 103 using the table of Table 1 or Table 2, thereby suppressing the influence of variations in the inductance value of the transformer 103 and outputting an output voltage in a wide voltage range with an inexpensive configuration. becomes possible. Note that the image forming apparatus to which the power supply unit 100, power supply unit 200, or power supply unit 300 of the present invention can be applied is not limited to the configuration illustrated in FIG. 6, and may be, for example, a color image forming apparatus. .

As described above, according to the fourth embodiment, it is possible to suppress the influence of variation in the inductance value of the transformer and to output in a wide voltage range with an inexpensive configuration.

3 CPUs
102 FETs
103 transformer 150 non-volatile memory

Claims (8)

a transformer having a primary winding and a secondary winding;
a switching element connected to the primary winding for turning on or off the voltage applied to the primary winding of the transformer according to the input pulse signal;
a control means for outputting the pulse signal to the switching element and controlling driving of the transformer;
A power supply device that outputs an output voltage according to the voltage induced in the secondary winding of the transformer,
storage means for storing information associating the output voltage with the duty and frequency of the pulse signal;
The power supply device, wherein the control means switches the frequency and/or the duty based on the output voltage and the information stored in the storage means. The information includes a first frequency corresponding to a first voltage range and a second frequency corresponding to a second voltage range continuous with the first voltage range,
When changing the output voltage within the first voltage range, the control means changes the duty of the pulse signal with the first frequency selected as the frequency of the pulse signal, and changes the duty of the second pulse signal. 2. The power supply device according to claim 1, wherein when the output voltage is changed within the voltage range, the duty of the pulse signal is changed while the second frequency is selected as the frequency of the pulse signal. The information includes a first duty corresponding to a first voltage range and a second duty corresponding to a second voltage range continuous with the first voltage range, and
When changing the output voltage within the first voltage range, the control means changes the frequency of the pulse signal with the first duty selected as the duty of the pulse signal, and changes the frequency of the pulse signal to change the second duty. 2. The power supply device according to claim 1, wherein when the output voltage is changed within the voltage range, the frequency of the pulse signal is changed while the second duty is selected as the duty of the pulse signal. A feedback means for receiving a feedback voltage corresponding to the output voltage,
The control means outputs a target value of the output voltage to the feedback means,
4. The method according to any one of claims 1 to 3, wherein the feedback means stops driving the transformer by the switching element regardless of the pulse signal when the feedback voltage is higher than the target value. The power supply device according to any one of claims 1 to 3. A detection means for detecting a current flowing through a load to which the output voltage is supplied,
The storage means stores a plurality of pieces of information according to the current flowing through the load,
The control means selects one of the plurality of information stored in the storage means according to the current detected by the detection means, and sets the duty and frequency of the pulse signal. The power supply device according to any one of claims 1 to 4. The storage means stores a plurality of the information according to temperature and/or humidity,
The control means selects one piece of information from a plurality of pieces of information stored in the storage means according to the temperature and/or the humidity, and sets the duty and frequency of the pulse signal. The power supply device according to any one of claims 1 to 4. an image carrier;
charging means for charging the image carrier;
exposing means for forming an electrostatic latent image on the image carrier charged by the charging means;
developing means for developing the electrostatic latent image formed by the exposing means to form a toner image;
a transfer means for transferring the toner image on the image carrier onto a recording material;
A power supply device according to any one of claims 1 to 6;
with
The image forming apparatus, wherein the power supply device supplies the output voltage to at least one of the charging device, the developing device and the transfer device. an image carrier;
charging means for charging the image carrier;
exposing means for forming an electrostatic latent image on the image carrier charged by the charging means;
developing means for developing the electrostatic latent image formed by the exposing means to form a toner image;
a transfer means for transferring the toner image on the image carrier onto a recording material;
environmental sensing means for sensing temperature and/or humidity;
The power supply device of claim 6;
with
the power supply device supplies the output voltage to at least one of the charging means, the developing means and the transfer means;
The image forming apparatus, wherein the control means selects one piece of information from the plurality of pieces of information based on the detection result of the environment detection means.

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